Mobile devices, such as mobile phones, are becoming increasingly popular. Such devices are often provided with wireless communications capabilities. In wireless communications, waveguide antennas are well-known and have been used in various applications.
Fifth generation (5G) is the next new standard for mobile communications. For the modern mobile device designs, a thinner phone design is a main stream in the industry. Moreover, a 5G system will adopt antenna array configuration for a good signal to noise ratio. However, a narrow beam width cannot cover a wide range link in the environment and therefore the requirement of multi-polarization can be used for scattering problems.
For polarization antennas, the most popular design is the waveguide antenna design. An open wave guide antenna is not appropriate for the design in a thin substrate since the substrate will confine the electric field; furthermore the return loss is bad. A traditional open waveguide antenna needs a wide aperture for power radiation and good return loss. However, the thin board design is not suitable for such waveguide antennas.